Vehicle vibration devices, in particular for vehicle seats, are formed such that they constitute an oscillating, sprung mounting between an upper part and a lower part, in this case between a vehicle seat part and a lower part of the vehicle seat subframe. For example a vehicle seat with a seat part can be connected to a lower part, that is attached to the vehicle cab floor or body of the vehicle, by means of scissor arms, wherein between the upper part and the lower part additional springing devices and/or damping devices are arranged in order to absorb by springing a vertically directed vibration introduced from outside into the vehicle seat system.
There are also horizontal vibration devices which serve to spring or damp out vibrations introduced into the vehicle seat system in the horizontal direction. For this the upper part of the vehicle seat is sprung mounted in the horizontal direction in relation to the lower part of the vehicle seat and can absorb by springing vibrations introduced in the horizontal or transverse direction.
Horizontal vibrations introduced into the system of the sprung vehicle seat or sprung vehicle cab frequently occur if a truck in which the vehicle seat or cab is arranged passes with its front wheels through a hollow or over a bump, and as a result the vehicle seat or vehicle cab briefly undergoes a braking or acceleration in the vehicle length direction in relation to the remainder of the vehicle. This is because, inter alia, the driver's weight is moved with a certain inertia, with a time delay or accelerated relative to the movement of the vehicle. A purely horizontal excitation occurs preferably for example in the case of a rigid subframe (unsprung vehicle) and a horizontal thrust, for example of a trailer e.g. by the overrun brake. Travelling over hollows and rocks with the front wheel preferably leads at least partly to a rotation movement about the contact point of the rear wheel with distance r (corresponds to the distance from the contact point to the seat surface). If the rear wheel then rolls over the unevenness, this also leads to a rotational movement about the contact surface or contact point of the front wheel. This thrust is preferably largely absorbed by vertical springing as this is virtually above the excitation point or contact surface of the rear wheel.
Frequently in such horizontally aligned vehicle vibration devices, the problem arises that the vibrations introduced into the system of a vehicle seat or vehicle cab can only be absorbed by springing in the direction parallel to the vehicle floor on which the vehicle seat is arranged. However a vehicle which for example with its front axle passes over a bump or raised road surface unevenness, in particular one or more stones, branches or similar, or through a hollow, does not exclusively undergo a brief change in its speed only in the horizontal direction. Rather, a type of tipping movement of the entire vehicle occurs, possibly associated with a slight deflection about an axis extending in the vehicle width direction.
On such a tipping movement or pitching, previous vehicle seats have the facility to absorb the vibrations introduced by springing as follows:
For the first degree of freedom of vibrations in the vertical direction (Z axis), a vehicle vibration device extending vertically in relation to the vehicle floor is provided between the vehicle seat upper part and the vehicle seat lower part. In addition damping devices can be installed in the vertical direction. For the vibrations introduced in the longitudinal horizontal direction in relation to the vehicle floor, according to the second degree of freedom (X axis) in the vehicle longitudinal axis direction, so-called horizontal vehicle vibration devices are present. For the third degree of freedom (Y axis) in the vehicle width direction, vehicle vibration devices acting in the horizontal direction can be present.
Thus previously three separate vehicle vibration devices have been provided for a total of three degrees of freedom along the X, Y and Z axes of a vehicle. The spring travels required to damp the vibrations introduced are always guided in the direction of the vehicle plane axes. Conventionally such spring travels are limited to around 100 mm extension in the vertical direction. The longitudinal and lateral horizontal spring travels depend on the design and safety requirements of the environment, and may be restricted by access to controls and scissor element settings. Such horizontally acting spring travels are usually limited to +/−25 mm in both the X axis and Y axis directions. A tipping or pitching movement of the vehicle cannot or can only be inadequately compensated by such separately arranged vehicle vibration devices in their spring travels because of the established degrees of freedom of the individual vehicle vibration devices.